A biosensor is a device for measuring the concentration of an analyte in a biological sample. A typical biosensor comprises a sensitive biological recognition element able to interact specifically with a target analyte, and a transducer or detector element that is able to transform the recognition event of the analyte with the biological element into a measurable signal. In contrast with conventional bioassays, biosensors allow the detection of molecular interactions as they take place, without requiring auxiliary procedures, making them highly attractive for biotechnological applications.
Among the various types of biosensors, field-effect transistor (FET) biosensors provide advantages in terms of miniaturization, standardization, mass-production, and a suitable configuration in which both the sensors and measurement circuits are integrated on the same chip. The FET biosensors, e.g., genetic FET biosensors, are particularly suited for the detection of charged biomolecules such as deoxyribonucleic acid (DNA).
In particular, the principle of genetic FET biosensors is based on the detection of a charge density change on the gate surface of the genetic FET, which is induced by the specific binding of DNA molecules to oligonucleotides probes. For instance, oligonucleotides probes are immobilized on the surface of a gate insulator of the genetic FET. When the genetic FET is immersed in a measurement solution comprising complementary DNA molecules, hybridization occurs at the surface of the gate area between the DNA molecules and the immobilized oligonucleotides. Since DNA molecules are negatively charged in an aqueous solution, the hybridization event can be detected by measuring a shift of the threshold voltage (Vt).
In order to achieve efficient immersion of the surface of the electrode area with the measurement solution, the electrode area of the genetic FET is typically integrated with a microfluidic channel for containing a flowing measurement solution. Nonetheless, molecular recognition events such as the hybridization and interaction of the charged biomolecules on the surface of the FET may be unreliable for the detection of certain analytes.
Accordingly, there exists a need in the art to overcome the deficiencies and limitations described hereinabove.